This in relates generally to inserts for use with prosthetic devices and is particularly directed to an air inflatable insert worn between a remaining limb and the socket of a prosthetic device.
The fitting of a prosthesis to the remaining stump of an amputated limb such as a leg involves insertion of the stump into a socket of the prosthesis. A spacer, or insert, provides a cushioning effect as well as tight fitting engagement with the prosthesis for the user. Prior art inserts generally suffer from a "piston effect", or relative movement between the stump and prosthesis, which results in irritation of the stump caused by excessive rubbing and pressure spots. Relative movement between the prosthesis and stump also limits control over the prosthesis and restricts user mobility in the case of a leg prosthesis.
Prior art prosthesis inserts take on various forms such as wool stockings or foam rubber attachments. These earlier inserts are formed integrally with the prosthesis or are attached thereto and are thus not removable. In some cases, a wedge-type structure is inserted between the limb stump and prosthesis socket in order to provide a tighter fit. A tight fit eliminates rubbing between the prosthesis and limb stump for improved comfort and reduces the aforementioned "piston effect" for improved prosthesis control. Another source of discomfort are pressure spots caused by contact between the boney and tender parts of the stump and the hard surface of the prosthesis socket. Excessive pressure for extended periods may result in skin ulcerations and infections, particularly for diabetics.
In order to increase comfort and improve control, prosthetic inserts are increasingly designed for individual use. These custom fitted inserts are attached to the prosthesis socket and are uniquely configured for individual use. These custom made inserts, which are not adjustable and expensive to fit, come generally in the form of cloth covered foam pads, air bladders, or fluid filled envelopes. The fluid may be in the form of a free flowing liquid or a gel. While affording a degree of custom fit, fluid filled inserts suffer from leakage problems and offer only a limited improvement in comfort because of the fluid incompressibility.
Air-filled inserts have also suffered from a lack of adjustability of fit and complicated and expensive fabrication procedures. Prior air inflated inserts have also been subject to leakage problems. One example of a pneumatic prosthetic permanent insert is disclosed in an article entitled "Improvement of the Air-Cushion Socket for Below-Knee Amputees" by Wilson et al, published in the Proceedings of the Second International Conference on Rehabilitation Engineering in 1984. This air cushion socket traps a layer of air in a pocket between a lower portion of the socket wall and an elastic sleeve enclosing the limb stump. A cotton loop disposed about the elastic sleeve is inserted in a narrow gap formed by the laminated socket and the distal edge of a brim disposed about the socket for allegedly preventing leakage of the air trapped in the pocket. U.S. Pat. No. 3,309,714 to Porten discloses a pneumatic cushion socket comprised of inner and outer layers of a pliant covering material, with a plastic foam sheeting material disposed between the covering material layers and secured to the inside of the inner wall of the socket. The resilient foam material has minute air spaces therein to permit air introduced under pressure between the inner and outer walls of the socket to fill microscopic interstices within the foam material. Although this approach employs air as a cushion, the primary cushioning effect is provided by the plastic foam sheeting material and thus affords only limited comfort and adjustability.
The present invention overcomes the aforementioned limitations of the prior art by providing a pneumatic prosthetic insert which provides pressure relief and a custom fit for any user of a prosthetic device. The inventive pneumatic prosthetic insert employes air inflatable voids and interconnecting passages disposed between facing inner and outer surface structures. The structure and material of the insert itself do not therefore provide any cushioning effect which is afforded solely by the trapped air.